What is the largest size to open up 1100 28" barrel gas ports for cycling light target loads. Loads r 3/4 oz, 12 ga., Extralite powder at 1250fps. these r skeet loads. u trap guys know more about reloading than all shooting sports put together. Thanks
You want to use step drills to do enlargen the ports, increasing the size in very small increments, and testing between each change.
The area of the ports is very small. A non-magnum 28" 2-3/4" field or trap barrel typically has two ports of .079" each, which is a #47 drill bit. The area of each port is .015398 square inches. Two give a combined total of .030796 square inches.
Going to the next step drill size of #46, which is .0810", results in a port are of .016187 square inches, total .032375 square inches. This may not sound like a lot, but it's an increase in total port area of 5%.
Jumping to a #45 step drill of .0820" results in a port size of .016589 square inches, total for two being .033179 square inches. This is a 7.7% increase in area.
A #44 step drill is .0860", giving a port size of .018247 sq in, total for two .036495 sq in. That's an increase of 18.5% in total port area.
#43 is .0890", port size .019543 aq in, total .039086 sq in. That's an increase of 27%.
You can see that #44 and #43 drills substantially increase the port area. This is why you should go only one step drill size at a time when you reach these sizes.
I would start with cleaning and checking the smallest possible step drill that fits the ports so you know what size you're starting with.
Let's assume it is a #47. It's not a huge increase to go to a #46 or #45 by drilling both ports, only 5% and 7.7%.
But there is a big step to #44 and especially #43, being 18.5% and 27%. I'd recommend increasing only one port at a time when going to these sizes.
Going further, I have a 30" fixed full 2-3/4" field or early flat rib trap barrel. Both ports have been enlargened to #44, which, again, is a 27% increase in area. It will easily cycle the lightest AA trap load, which is the AAL127 which is 1 oz 2-3/4 dram at 1180 fps. My regular 2-3/4" 1100 or 1187 field barrels will not cycle this load.
The flip side of the coin is I found when using the heaviest trap loads, and cheap promo loads, the bolt velocity is high and there is a noticeable increase in recoil, giving a sharp rap. The point being that I'm not so sure that opening up the ports this large is a wise idea if you ever intend to shoot heavy trap loads.
EuroJoe has good advise. Opening the ports is a one way deal. If you reduce the resistance needed to cycle the gun by slowly cutting the recoil spring you may arrive at a length where it will cycle light loads. It would only cost you the price of a new recoil spring, which is about $5 to find out. If you do as suggested, and cut 1/4" at a time you'll probably get a length that will work good for both light and heavy loads. It "may" take an inch or so but go slow.